STS-134: Endeavour’s slip to aid AMS change – New EVA protocol in work

December 6, 2010 by Chris Bergin

NASA managers are realigning Endeavour’s processing flow milestones, as her launch date slips to an interim placeholder of April 1, 2011. Although the original late February launch date was fully supported by all the hardware elements participating in STS-134, the slip allows for extra contingency time for late changes to be carried out on the AMS-02 (Alpha Magnetic Spectrometer-02) payload.

STS-134 Processing Latest:

Endeavour was set to rollover from her Orbiter Processing Facility (OPF-2) in January, following what is currently a very smooth flow, with only 20 IPRs (Interim Problem Reports) charged against the fleet’s youngest orbiter during what is her final preparations for a mission.

Last week, Endeavour’s engineers completed the positive pressure testing on the orbiter, whilst working preparations for GN2 servicing. This work is currently coming to the end of a three day decay check.

The issue “MEI acoustic sensor V08Y9704A would not channelize”, has resulted in troubleshooting being carried out over the last couple of weeks. Engineers believe they have found the problem – a bad connector – as a root cause, but will continue to evaluate.

“Troubleshooting is complete to date. All continuity checks are complete. Engineering suspected a bad connector at the door break. Further disposition to finish final system checkout,” noted the NASA Test Director (NTD) report (L2). “Engineering is evaluating further troubleshooting.

Endeavour continues to be in final rollover preparations and closeouts, despite the delay to her mission, with only Wing Leading Edge “end-to-end” testing scheduled for the first part of this week.

With the mating of ET-122 and the twin Solid Rocket Boosters (SRBs) also slipping to next year, only a working date of January 11 has been listed for the milestone by Ground Operations this week, pending program direction.

Some inspections on ET-122’s LOX/Intertank flange stringers have also taken place inside the Vehicle Assembly Building (VAB), utilizing the additional access of the checkout cell in High Bay 4E (HB-4E).

“SRB BI-145/RSRM 113 (VAB HB-3): S0003 ET Mate is TBD (To Be Determined) pending program direction. The working date is January 11, 2011,” added the NTD report. “ET-122 (VAB HB-4E): PDL (foam) application to the crushed foam area on the LH2 feedline support bracket is complete.

“The ET/IT access kit removal and inspection is in work. Pre-move inspections will be complete prior to the mate decision. Preparations for ET lift from the checkout cell will be worked after pre-move inspections.”

Endeavour’s mission continues to be refined – as is usual – by managers within MOD (Mission Operations Directorate) at the Johnson Space Center, in cooperation with the ISS management on the Space Station Program Control Board (SSPCB).

“At SSPCB, there was discussion on the in-suit light exercise protocol. The current plan is to use EVA-3 on STS-134 for the demo of that protocol, then evaluate it and figure out whether to keep it as another option,” noted MOD on the latest Shuttle Standup/Integration Report (L2).

“The NESC (NASA Engineering and Safety Center) is reviewing the protocol and expected to have their review complete by mid-December. Will schedule STS-134 flight rules to a JPRCB (Joint Program Requirements Control Board) meeting in mid-January.”

The addition is related to a change in the pre-breath protocol, which will drastically change the preparations a spacewalker would need to undergo ahead of an EVA.

“Assessing the use of a new EVA pre-breathe protocol for EVA 3. Phase V-5 EVA pre-breathe protocol (also referred to as In Suit Light Exercise (ISLE) protocol does not require overnight campout or CEVIS (Cycle Ergometer Vibration Isolation System) exercise). ISLE exercise is equivalent to walking a mile in 70 minutes,” noted the MOD presentation.

“Latest version of Phase V-5 includes a 10.2 depress/repress cycle which was not included in early versions. Other ISLE benefits include the following: Crew is not isolated in the A/L (Air Lock) overnight allowing for a more “normal” night before and morning of EVA. Expected to save around 6 lbm O2 per EVA (13 lbm vs 19 for campout). Less crew time on PHA mask.”

Managers have taken the ISLE protocol through the same set of boards that previously review and approved exercise pre-breathe protocols, with the Flight Activities Control Board and NESC all providing initial approval for the ‘experiment’ to take place ahead of STS-134’s EVA-3.

The meeting in mid-December is expected to provide the final approval to insert the protocol into STS-134, while holding on to the fallback position of a standard campout protocol for EVA 3 if the “products” do not come together.

The slip to STS-134’s launch date also aids a late change on the primary payload of AMS-02 – although the original launch date would have still provided two week’s worth of margin in the flow for the alterations.

The AMS-02 unit, with a mass of over 15,000lbs – was originally without a ride to orbit until the United States Congress mandated its addition to the Shuttle manifest. The payload will be attached to the Starboard 3 Upper Inboard Command Attach System (CAS) on the ISS.

AMS-02 unit is a particle physics detector, designed to search for antimatter and the origin and structure of dark matter, thus gaining huge support from the scientific community, whilst providing yet another remarkable legacy to Endeavour’s contributions to the human race’s understanding of the universe.

“AMS hardware updates: Cryo magnet change-out and extended thermal/life cycle testing has been completed. AMS collaboration made the decision to upgrade 22 Printed Circuit Boards (PCB) in the Power Distribution System (PDS),” noted a large MOD presentation (L2) updating the mission’s status.

“AMS-02 switched from the cryogenic magnet to the AMS-01 permanent magnet. Excessive heat transfer confirmed with cryo magnet system testing. Significant reconfiguration of the payload to make this change,” noted the MOD presentation, which went into an in-depth review of what has been a successful change.

While the changeout was required due to test results prior to the shipping of AMS to the Kennedy Space Center (KSC), MOD are happy the changes were made from their own operational standpoint.

“Simplifies operations for MOD: No longer any LCCs (were required due to cryo system). No longer any ascent commanding (was required due to cryo system). Reduced time criticality to get activated (cryo system was a consumable = limited lifetime).”

With NASA happy the new configuration of AMS will support the extension of the ISS to 2020, only one further change was ordered – relating to the PCBs in the PDS – due to the extended lifetime of the orbital outpost.

“AMS-02 cryo magnet change-out has been successfully completed as planned. The collaboration has performed extended thermal/life cycle testing due to the ISS extension to 2020 (and perhaps beyond). Although no failures have occurred, the collaboration has decided to upgrade some Printed Circuit Boards (PCB) in the Power Distribution System (PDS),” added the MOD presentation.

“Concern over the extended life for potential impact of micro-cracks that formed in solder joints. The PCBs being replaced are on the output or payload side of the PDS- the input or Shuttle/ISS side are not affected and will not be touched.

“AMS mission success/mission assurance item only, no Shuttle or ISS impact. Total of 22 PCBs to be replaced. Schedule supports February 27th launch with – 2 weeks margin. Only impact to MOD was to move AMS Install sim from Dec 20th to Dec 16th to ensure AMS personnel support.”

Expanding on the change, the presentation went on to list the improvements that are being made ahead of its ride uphill with Endeavour.

“The following upgrades are being implemented to improve thermal performance and provide better assurance that the PDS lifetime will exceed the ISS lifetime: The Mounting Brackets will be changed from Aluminum to Copper-Berylium to better match the Coefficient of Thermal Expansion (CTE) of the Cu-Be housings of the Mosfets & Diodes.

“Gap alignment & tolerance between components will be improved. Mating surfaces will have Chotherm and Therm-a-Form added. Soldering configuration will be upgraded with the addition of a rivet and double-sided thru-hole joints.

“No active components will be replaced. The upgrade will be presented to the Shuttle Program, ISS Program, JSC PSRP and ISS SRP.”

The original manufacturer in Italy will carry out the upgrades before shipping them into KSC for installation into AMS. No impacts were expected from the previous late February launch date, though that margin has been relaxed yet further with the slip to the April 1 placeholder.

“The upgrades will be performed by the original manufacturer, Carlo Gavazzi Space in Italy. They already have all the facilities, materials, parts, personnel, test, inspection, and support resources required,” the presentation added.

“They have already done several upgrades to non-flight qualification boards to assure success when the flight boards are received. Extensive static, vibration, thermal cycle and functional tests of non-flight boards & components have and are being done to qualify the process.

“Thermal, vibration, and functional testing will be done at a board level. Functional testing will be repeated at the systems level. The upgrade is being monitored daily by experts from CERN, MIT, & INFN. Results thus far indicate the planned delivery dates and technical requirements will be met. The progress will be regularly reported to JSC.”